Double-walled contained shear valve, particularly for fueling environments

ABSTRACT

A double-walled contained shear valve comprises of an inner housing forming a fuel flow path, and a containment housing surrounding the inner housing, either partially or wholly, to provide a secondary containment. An interstitial space is formed between the inner housing and the containment housing as a result, and may be placed under a vacuum or pressure level to monitor for leaks. A vacuum actuator coupled to the interstitial space automatically opens and closes the fuel flow path of the shear valve in response to the vacuum level in the interstitial space to prevent leaks to the environment. The shear valve may contain a flange for connection to internal fuel dispenser piping that either does or does not includes interstitial space orifices to couple the shear valve interstitial space to the fuel dispenser piping interstitial space to monitor the vacuum or pressure level in these interstitial spaces as one contiguous space.

RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationNo. 60/654,390 entitled “DOUBLE WALL CONTAINED SHEAR VALVE, PARTICULARLYFOR FUELING ENVIORNMENTS,” filed on Feb. 18, 2005, and incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a double-walled contained shear valve,particularly for use in fueling environments, wherein the shear valve iscomprised of a fuel flow path surrounded by an interstitial space toprovide secondary containment and leak detection/prevention. Thedouble-walled shear valve is designed to close the fuel flow path inresponse to either a shear or a loss of vacuum in the interstitial spaceor other system having a separate interstitial space.

BACKGROUND OF THE INVENTION

In service station environments, fuel is delivered to fuel dispensersfrom underground storage tanks (UST), sometimes referred to as fuelstorage tanks. USTs are large containers located beneath the ground thathold fuel. A separate UST is provided for each fuel type, such as lowoctane gasoline, high-octane gasoline, and diesel fuel. In order todeliver the fuel from the USTs to the fuel dispensers, typically, asubmersible turbine pump (STP) is provided that pumps the fuel out ofthe UST and delivers the fuel through a main fuel piping conduit thatruns beneath the ground in the service station. Other types of pumpsother than a STP, such as a self-contained pump within the dispenserhousing for example, may be employed.

Due to environmental and possible regulatory requirements governingservice stations, the main fuel piping conduit is usually required to bedouble-walled piping. Double-walled piping contains an inner piping thatcarries the fuel. An outer piping forming an outer annular space, alsocalled an “interstitial space,” surrounds the inner piping so as tocapture and contain any leaks that occur in the inner piping, so thatsuch leaks do not reach the ground. An example of double-walled fuelpipe is disclosed in U.S. Pat. No. 5,527,130, incorporated herein byreference in its entirety.

It is possible that the inner piping of the double-walled fuel pipingcould fail, thereby leaking fuel to the interstitial space of thedouble-walled fuel piping. Or, it is possible that the outer piping ofthe double-walled fuel piping could fail thereby leaking fuel capturedin the interstitial space. In either scenario, without monitoring of thedouble-walled fuel piping interstitial space, it is possible that a leakin the double-walled fuel piping will go undetected for some period oftime. The STP will continue to operate as normal, drawing fuel from theUST; however, the fuel may leak to the ground instead of being deliveredto the fuel dispensers.

Recent proposed changes in state and federal regulations will tightenthe requirements to contain leaks and will further require better leakdetection so that environmental damage may be minimized. As a result, itis becoming imperative that all potential leak sources be evaluated andsteps taken to detect and contain leaks in the piping systems.

Methods of monitoring the interstitial space of fuel piping aredisclosed in U.S. Patent Application Publication Nos. 2004/0045343;2004/0149017; and 2004/0182136, which are all hereby incorporated byreference in their entireties. In these systems, a vacuum-generatingsource, which may be the STP, draws a vacuum in the interstitial space.Thereafter, the interstitial space is monitored for pressure changes. Ifsufficient pressure changes occur, this is an indication that either theinner piping or the outer piping of the double-walled fuel piping hasincurred a leak or breach. The leak or breach could have occurred in anybranch or zone of the fuel piping in which the interstitial space isbeing monitored.

Double-walled fuel piping is located outside of the fuel dispenserbeneath the ground in conduits that deliver fuel from the STP to thefuel dispensers. Main fuel piping delivers fuel underneath the fueldispensers. Double-walled branch fuel piping, typically located within adispenser sump located beneath ground under individual fuel dispensers,connects the individual fuel dispensers to the main fuel piping toreceive fuel for dispensing through its respective hose and nozzle.However, as illustrated in FIG. 5 of U.S. Pat. No. 5,713,607,incorporated herein by reference in its entirety, the interstitial spaceof the double-walled branch fuel piping, or riser pipe “P_(R),”terminates on the inlet side of the shear valve “V_(S)”. Therefore, theinterstitial space, if monitored, is only monitored to a point thatstops before the inner fuel piping couples to the shear valve.

Fuel dispensers also contain internal fuel piping or conduits that carrythe fuel from the outlet side of the shear valve through variouscomponents, such as valves and meters, internal to the fuel dispenserbefore the fuel exits through the hose and nozzle into a vehicle fueltank. This dispenser internal fuel piping is not double-walled fuelpiping; however, the internal fuel piping can incur a breach as well. Ifthis internal fuel piping is not contained and monitored, the leak cancontinue to occur without notification, and the STP will continue tooperate as normal, drawing fuel from the UST and possibly leaking fuelto the ground. A solution to this issue is provided in U.S. PatentApplication Publication No. 2004/0261504, which is hereby incorporatedherein by reference in its entirety (hereinafter the “'504application”).

In the '504 application, a double-walled shear valve is provided betweendouble-walled branch fuel piping located beneath the fuel dispenser anddouble-walled fuel piping located internal to the fuel dispenser so thatthe interstitial space of the branch fuel piping is coupled to theinterstitial space internal fuel piping for monitoring of breaches orleaks in the fuel piping. Further, by providing a secondarily containedshear valve, the interstitial space around the shear valve can bemonitored for breaches or leaks as well.

Therefore, as discussed in the '504 application, it may be desirable toprovide secondary containment of the internal fuel piping to the fueldispenser so that breaches that occur in the internal fuel piping arealso contained. Further, it may be desirable to monitor the secondarycontainment space of the internal fuel piping so that breaches thatoccur in either the inner or outer fuel piping are detected for thereasons stated above. However, any fuel piping, fittings or couplings,such as the shear valve for example, that are not secondarily containedprovide a failure point in the system where a leak will not becontained.

Further, if it is desirable to use the same vacuum generating sourcethat draws a vacuum in the main and/or branch fuel piping interstitialspace as the vacuum generating source to draw a vacuum in theinterstitial space of the internal fuel piping, the interstitial spaceof the internal fuel piping must be fluidly coupled to the interstitialspace of the branch and/or main fuel piping. Otherwise, a separatevacuum generating source will be required.

Therefore, the present invention provides a double-wall contained shearvalve to solve one or more of the aforementioned problems which are alsodisclosed in the '504 application. The first problem is that fuel thatleaks at the shear valve will not be contained even if the branch fuelpiping located on the inlet side of the shear valve, or the internalfuel dispenser piping located on the outlet side of the shear valve, isdouble-walled piping. A double-walled shear valve must be used thatstill shears properly in the event of an impact even with double-walledcontainment. A double-walled contained shear valve can provide aninterstitial space around the inner housing of the shear valve formonitoring any leaks or breaches in the inner or containment housings ofthe shear valve for the reasons stated above. The third problem is thatthe shear valve's fuel flow path should be closed in response to a leakto prevent further leakage.

SUMMARY OF THE INVENTION

The present invention is directed to a double-walled shear valve,preferably for use in a fuel dispenser. The double-walled shear valvecontains an inner housing forming a fuel flow path. An outer housing orcontainment housing is provided that surrounds either partially orwholly the inner housing to provide a second containment. Thecontainment housing may also provide part of the fuel flow path. Aninterstitial space is formed between the inner housing and thecontainment housing. In this manner, a leak that results due to breachof an inner housing of the shear valve may be contained within theinterstitial space between the inner and containment housing instead ofleaking to the environment.

The interstitial space can further be placed under a vacuum or pressure.The vacuum or pressure level within the interstitial space is monitoredto detect breaches in either the inner housing or the containmenthousing of the shear valve, which may be caused by a shear of the shearvalve for example. The interstitial space is monitored for pressure orvacuum level variations. If the pressure or vacuum level varies beyondthresholds or expectations, a leak may be present.

In another embodiment of the invention, the double-walled shear valvecontains a vacuum actuator. The vacuum actuator is coupled to theinterstitial space of the double-walled shear valve. The vacuum actuatorresponds to generation of vacuum levels or loss thereof in theinterstitial space or other system having a separate interstitial space.When a sufficient vacuum level is maintained, the vacuum actuator keepsa main poppet valve within the fuel flow path of the shear valve open toallow fuel to flow through the shear valve. The main poppet valve iskept open as long as a sufficient vacuum level is maintained in theinterstitial space. If a leak or shear occurs, the interstitial spaceloses vacuum level. In response, the vacuum actuator automaticallycauses the main poppet valve to close thereby closing off the fuel flowpath within the shear valve to prevent fuel from leaking to theenvironment. Once a sufficient vacuum level is restored in theinterstitial space, the vacuum actuator automatically reopens the mainpoppet valve to open to allow fuel to flow through the shear valve onceagain.

In another embodiment of the invention, the double-walled shear valve isfitted with a main poppet valve that can be opened by the vacuumactuator with less force than normally required once the vacuum level inthe interstitial space is restored. For example, if there is pumppressure trapped on the upstream side of the main poppet valve andlittle or no pressure or atmospheric pressure on the downstream side,more force than can be provided by the vacuum actuator may be requiredto open the main poppet valve once the vacuum level in the interstitialspace is restored. The main poppet valve contains an inner diameter sealfitted to an inner diameter tube coupled to the downstream side of thevalve. Once the inner diameter seal is opened, the inner diameter tubeis coupled to the upstream side of the main poppet valve to begin toequalize pressure across the main poppet valve. The inner diameter tubehas a diameter less than the diameter of the fuel flow path. Thus, lessforce is required to open the inner diameter seal than to open the mainpoppet valve seal, because the main poppet valve seal rests against theentire, larger diameter of the fuel flow path. When the inner diameterseal is opened, the pressure differential between the upstream anddownstream side of the main poppet valve starts to equalize. As thisequalization occurs, the force required to open the main poppet valveseal is lessened thereby allowing the vacuum actuator to completely openthe main poppet valve and thus reset the shear valve to an operationalcondition.

The shear valve may also be designed to allow automatic coupling of itsinterstitial space to the interstitial space of a branch fuel pipingand/or internal fuel dispenser piping when such fuel piping is coupledto the shear valve. In this manner, a monitoring system that is used tomonitor the interstitial space of fuel piping can also be used tomonitor the interstitial space of the shear valve as one singlemonitored zone.

In another embodiment of the invention, the interstitial space of thedouble-walled shear valve is blocked from extending beyond the outlet ofthe shear valve. In this manner, the interstitial space of the shearvalve is not coupled to an interstitial space of the internal fueldispenser piping. Thus, a monitoring system that monitors the pressureor vacuum level of the double walled shear valve is not designed orintended to also monitoring of the interstitial space of the internalfuel dispenser piping. For example, it may be desired to sell thisversion of the double-walled shear valve to customers that either do notsupport or are not authorized to support the monitoring of the internalfuel dispenser piping.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing figures incorporated in and forming a part ofthis specification illustrate several aspects of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is an exemplary illustration of a double-walled contained shearvalve in accordance with the present invention;

FIG. 2 is an illustration of the shear valve illustrated in FIG. 1 froma top angled view to show the top of the shear valve;

FIG. 3 is a cross section illustration of the shear valve illustrated inFIG. 1;

FIG. 4 is an cross section illustration of the shear valve illustratedin FIG. 1 from a top angled view to show the top of the shear valve;

FIG. 5 is a bottom angled view of the downstream housing of the shearvalve illustrated in FIGS. 1-4;

FIG. 6 is an illustration of the containment or outer housing of theshear valve illustrated in FIGS. 1-4;

FIG. 7 is a top angled view of the upstream housing of the shear valveillustrated in FIGS. 1-4;

FIG. 8 is an illustration of a fuel dispenser;

FIG. 9 is an illustration of the fuel dispenser illustrated in FIG. 8showing the internal components of the fuel dispenser and the interfacebetween the shear valve, the branch fuel piping, and the fuel dispenserinternal fuel piping;

FIG. 10 is an illustration of a second embodiment of the double-walledcontained shear valve;

FIG. 11 is an illustration of the shear valve illustrated in FIG. 10attached to fuel piping;

FIG. 12 is a cross section illustration of the shear valve illustratedin FIG. 10 with the main poppet valve closed to disallow fuel flow inresponse to a shear or loss of vacuum;

FIG. 13 is an illustration of the vacuum actuator linkage mechanism toopen and close the main poppet valve of the shear valve illustrated inFIG. 10;

FIG. 14 is a cross section illustration of the shear valve illustratedin FIG. 10 with the main poppet valve open to allow fuel flow;

FIG. 15 is an illustration of the downstream housing of the shear valveillustrated in FIG. 10;

FIG. 16 is an illustration of the containment or outer housing of theshear valve illustrated in FIG. 10;

FIG. 17 is an illustration of the upstream housing of the shear valveillustrated in FIG. 10;

FIG. 18 is an illustration of the coupling of the interstitial space ofthe shear valve illustrated in FIG. 10 with an interstitial space ofinternal fuel piping to provide one continuously interstitial spacetherebetween;

FIG. 19 is an illustration of an alternative embodiment of the shearvalve illustrated in FIG. 10 with the interstitial space of the shearvalve blocked from extending through the downstream housing; and

FIG. 20 is an illustration of the downstream housing used in the shearvalve illustrated in FIG. 19.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments set forth below represent the necessary information toenable those skilled in the art to practice the invention and illustratethe best mode of practicing the invention. Upon reading the followingdescription in light of the accompanying drawing figures, those skilledin the art will understand the concepts of the invention and willrecognize applications of these concepts not particularly addressedherein. It should be understood that these concepts and applicationsfall within the scope of the disclosure and the accompanying claims.

The present invention is directed to a double-walled shear valve,preferably for use in a fuel dispenser in a fueling environment. Theshear valve contains an outer or containment housing to provide a secondcontainment around an inner housing. The inner and containment housingsalso contain orifices within that are coupled together to provide a fuelflow path through the shear valve. An interstitial space is formedbetween the inner housing and the containment housing. In this manner, aleak that results due to a breach of the inner housing of the shearvalve is contained within the interstitial space between the inner andcontainment housings.

The interstitial space can further be placed under a vacuum or pressure.The vacuum or pressure level within the interstitial space is monitoredto detect breaches in either the inner housing or the containmenthousing of the shear valve, and/or a shear of the shear valve. Forexample, if a vacuum is applied to the interstitial space of the shearvalve, the interstitial space can be monitored for pressure variations.A vacuum actuator controls the opening and closing of a main poppetvalve located inline to the fuel flow path of the shear valve inresponse to vacuum generation and loss in the interstitial space orother system having a separate interstitial space.

The shear valve in accordance with one embodiment of the presentinvention is illustrated in the external view diagram in FIG. 1. In FIG.1, the shear valve (generally designated as element 10) is illustratedfrom a side view. The shear valve 10 is comprised of three housingsfitted together to form one shear valve 10. The shear valve 10 iscomprised of a downstream housing 12, which is coupled to a containmenthousing or containment housing 14, which in turn is coupled to anupstream housing 16. This patent application will describe the innerconnections between these housings 12, 14, and 16 in FIG. 3 below.

An orifice (not shown in FIG. 1) in the upstream housing 16 provides aninlet 17 for fuel to flow from the underground storage tank (not shownin FIG. 1) through an internal fuel flow path (not shown in FIG. 1) ofthe shear valve 10. The fuel that flows through the inlet 17 through thefuel flow path internal to the shear valve 10 exits through an outlet 18that is formed by an orifice 26 (shown in FIG. 2) in the downstreamhousing 12.

A leak skirt 19 is provided around a portion of the containment housing14 so that any fuel that leaks around the shear groove (illustrated inFIG. 3) is prevented from leaking to the environment in the event thatthe shear valve 10 incurs an impact or other force causing a shearing.Mounting bosses 20, 22 are attached or provided as part of thecontainment housing 14 to mount the shear valve 10 in place wheninstalled in the field, as is well known to one of ordinary skill in theart. The shear valve 10 may also contain an interstitial space port 277(illustrated in FIG. 17) that is fluidly coupled to the interstitialspace formed between the outer housing 14 and the downstream andupstream housings 12, 16 as illustrated in FIG. 3. This allows a vacuumor pressure-generating source to generate a vacuum or pressure in theinterstitial space around the shear valve 10 for monitoring, asdescribed above and in the '504 application, to test the integrity ofthe housings 12, 14, 16 and the interstitial space around the shearvalve 10 for detection of breaches or leaks.

FIG. 2 illustrates the shear valve 10 illustrated in FIG. 1, except thatthe illustration is from the perspective of a top angle view to show thetop of the shear valve 10 and the components and structure of thedownstream housing 12. The downstream housing 12 consists of a flange 24that contains an orifice 26 in approximately the center of the flange24. The orifice 26 forms a fuel flow path 28 through the downstreamhousing 12. This fuel flow path 28 is coupled to the fuel flow path thatis formed by the upstream housing 16, as will be illustrated moreclearly in FIG. 3. The orifice 26 in the flange 24 forms an inner wall30 that has a thickness shown as ‘W’, also show as element 34. Theflange 24 also contains an outer wall 32 having the same thickness onits outer edge.

FIG. 2 shows a secondary poppet stem 35, that may be spring loaded, thatis attached to a secondary poppet valve 98 (illustrated in FIG. 3) thatmoves downward against a secondary poppet seat 37 (illustrated in FIG.3) when a shear occurs similar to that disclosed in U.S. Pat. No.5,244,006, incorporated herein by reference in its entirety. The flange24 of the downstream housing 12 contains one or more orifices 36 thatare used to secure the flange 24 to fuel piping that may be internal tothe fuel dispenser (not shown) in a tight manner, using bolts or variousother fastening means, so that the fuel flowing through the fuel flowpath 28 enters into the fuel piping connected to the flange 24. Theflange 24 also contains grooves 38, 42 on the top surface of the flange24 that are designed to hold an o-ring in place and against a matingfuel piping connection (not shown) so that a tight seal is formedbetween the outlet 18 of the shear valve 10 and a mated fuel piping.

The flange 24 also contains one or more orifices, called interstitialspace orifices 40, that are fluidly coupled to the interstitial spaceformed between the containment housing 14 and the upstream anddownstream housings 12, 16 as will be described in FIG. 3. This is so aninterstitial space 60 (illustrated in FIG. 3) of the shear valve 10 canbe fluidly coupled to fuel piping that is connected to the flange 24 toform one continuous interstitial space therebetween. In this manner, aleak detection or monitoring system can draw a vacuum or pressurize theinterstitial space orifice 40/interstitial space 60 and monitor theinterstitial space 40/60 around the shear valve 10 and fuel piping asone contiguous space.

FIG. 2 also shows a third mounting boss 44, which in combination withmounting bosses 20, 22, allows the shear valve 10 to be physicallyattached and/or held into place when installed. A support beam or bar(not illustrated) is placed in between mounting bosses 20, 44 andmounting boss 20 so that the mounting bosses 20, 22, 44 surroundinterior space formed by the mounting bosses 20, 22, 44 to support theshear valve 10. FIG. 2 also shows orifices 46 in the upstream housing 16that allow the shear valve 10 and its fuel flow path 28 to branch fuelpiping located beneath the ground, which, in turn is coupled to the mainfuel piping.

FIG. 3 illustrates a cross section illustration of the shear valve 10illustrated in FIGS. 1 and 2. The upstream housing 16 is comprised of auniform body that contains an internal orifice forming an upstreamhousing flow path 92. The thickness of the material comprising theupstream housing 16 provides an inner wall 48 and an outer wall 50.Similarly, the containment housing 14 contains an orifice formingcontainment housing flow path 94, wherein the thickness of the materialcomprising the containment housing 14 forms an inner wall 52 and anouter wall 54.

The containment housing 14 is secured to the upstream housing 16 by athreaded male outer edge 56 of the containment housing 14 that isscrewed securely into a threaded female groove 58 formed as part of theupstream housing 16. The female threaded groove 58 contains anindentation 59 around its edge whereby an o-ring seal 61 is providedtherein to provide sealing between the threaded groove 58 and thethreaded outer edge 56 thereby sealing off the downstream housing flowpath 96 and the interstitial space 60, between the outer wall 68 and theinner wall 52, from each other. Note that the connections between theouter containment housing 14 and the upstream housing 12 are shown asthreaded connections, but may be provided as any other type ofconnection, including but not limited to a pin connection.

When the upstream housing 16 is secured to the containment housing 14 inthis manner, an interstitial space 60 is formed between the outer wall50 of the upstream housing 16 and the inner wall 52 of the containmenthousing 14. The upstream housing 16 provides interstitial space orifice62 that is fluidly coupled to the interstitial space 60 so that pipinghaving an interstitial space that is connected to the upstream housing16 can fluidly couple its interstitial space with the interstitial space60 of the shear valve 10 to form one continuous space. Likewise, inorder to maintain the fluid coupling of the interstitial space 60throughout the shear valve 10, the containment housing 14 also containsan interstitial space orifice 62 that couples to interstitial space 60.

Also, the containment housing 14 has a threaded female groove 63,similar to threaded female groove 58 in the upstream housing 16, thatmates with a male threaded outer edge 65, to assist in securing theupstream housing 16 to the containment housing 14 just as describedabove. Again, the threaded outer edge 65 is provided with an indentation67 to allow an o-ring seal 69 to placed therein to provide a seal justas described above.

The outer surface of the upstream housing 12 also contains grooves 104,106, similar to grooves 38, 42 on the flange 24 of the downstreamhousing 12, that are designed to hold o-rings in place and against amating fuel piping connection (not shown) so that a tight fit is formedbetween the inlet 17 of the shear valve 10 and a mated fuel piping.

The downstream housing 12 contains an orifice that forms a downstreamhousing fuel flow path 96 that is fluidly coupled to the outer housingflow path 94 and the upstream housing flow path 92. The downstreamhousing flow path 96 is only coupled to the outer housing flow path 94and upstream housing flow path 92 when the poppets 82, 92 are open. Dueto the thickness of the material comprising the downstream housing 12,the downstream housing 12 has an inner wall 66 and an outer wall 68.

Just as provided for the connection between the containment housing 14and the upstream housing 16, the containment housing 14 is also securedto the downstream housing 12 in a similar fashion. The outer containmenthousing 14 contains a female threaded groove 70 in which a threaded maleouter edge 76 of the downstream housing 12 is screwed into to form atight fit between the outer containment housing 14 and the downstreamhousing 12. The female threaded groove 70 contains an indentation 72around its edge whereby an o-ring seal 74 is provided therein to providea sealed fit between the threaded groove 70 and the threaded outer edge76 thereby sealing off the downstream housing flow path 96 and theinterstitial space 60, between the outer wall 68 and the inner wall 52,from each other. Note that the connections between the outer containmenthousing 14 and the downstream housing 12 are shown as threadedconnections, but may be provided as any other type of connection,including but not limited to a pin connection.

Also, the containment housing 14 has a threaded female groove 77 thatmates with a male threaded outer edge 79, to assist in securing thedownstream housing 12 to the containment housing 14 just as describedabove. Again, the threaded outer edge 79 is provided with an indentation81 to allow an o-ring seal 83 to placed therein to provide a seal justas described above.

The containment housing 14 contains a shear groove 78 on the outer wall54 to provide a shearing or impact or break point for the shear valve 10to break or shear in a controlled fashion when impacted. The sheargroove 78 extends around the circumference of the containment housing14. In the event of a shear at the shear groove 78, fuel that may becaptured in the interstitial space 60 may leak outside the outer housing14. Therefore, the leak skirt 19 is provided around the circumference ofthe shear groove 78 and proximate to the shear groove 78 wherein a leakcontainment chamber 80 is formed to capture any leaks that may occur asa result of shearing at the shear groove 78. The leak skirt 19 may bemanufactured out of any elastic or elastomer material.

The shear valve 10 contains a main poppet 82 comprised of a main poppethead 84 and a carrier 86 similar to the shear valve disclosed in U.S.Pat. No. 5,244,006, previously referenced and incorporated herein. Thecarrier 86 is connected to a rotatable shaft 88 that is coupled to theupstream housing 16 of the shear valve 10. The rotatable shaft 88 isspring-loaded (not shown) and attached to a fuseable link (notillustrated) contained external to the shear valve 10. When a shearingor other impact occurs on the shear valve 10, the force in the spring isreleased, causing the main poppet valve 82 to move upward toward a mainpoppet valve seat 90, wherein the main poppet valve head 84 is pushedsecurely against the main poppet valve seat 90. This cuts off theupstream housing flow path 92 from containment housing flow path 94 sothat fuel cannot leak above the upstream housing flow path 92.

A secondary poppet valve 98 is provided in the downstream housing 12such that when fuel flows through the upstream housing flow path 92 andthrough the outer housing flow path 94, the force of the fuel flowpresses against a secondary poppet head 100 of the secondary poppetvalve 98 to push the secondary poppet head 100 upward. This allows thefuel to flow around and out of the outlet 18. In the event of a shear orother impact to the shear valve 10, the shear valve 10 is designed sothat the downstream housing 12 will separate from the containmenthousing 14. In this event, the secondary poppet stem 35 of the secondarypoppet valve 98 is pulled downward due to its bias such that thesecondary poppet valve head 100 is pushed securely tight against thesecondary poppet valve seat 37. This prevents fuel in fuel pipingcoupled to the flange 24, outlet 18, and/or and downstream housing flowpath 96 from flowing backward into the containment housing flow path 94.

Therefore, as illustrated in FIG. 3, the shear valve 10 providessecondary containment of the fuel flow path formed by the coupling ofupstream housing flow path 92 to containment housing flow path 94 todownstream housing flow path 96. If a leak occurs in the upstream ordownstream housings 16, 12, the leak will be contained in interstitialspace 60 formed between these housings 16, 12 and the containmenthousing 14. Additionally, via interstitial space orifices 64 and 40, theinterstitial space 60 in the shear valve 10 can be coupled to theinterstitial space of piping that is connected to the upstream housing14 and/or the downstream housing 12, so that the interstitial space 60of the shear valve 10 and the interstitial space of the fuel piping canbe fluidly coupled together to monitor the coupled interstitial space 60as one continuous space.

FIG. 4 illustrates the shear valve of FIG. 3 as a cross-sectionillustration of shear valve 10 from a top angle view perspective. FIG. 4does not show any additional elements that are not described andillustrated in FIG. 3; however, the drawing provides a depth perceptionof the interstitial space 60 and how the interstitial space 60 surroundsthe outer wall 50 of the upstream housing 16 and the outer wall 68 ofthe downstream housing 12.

FIG. 5 is a bottom angle view of the downstream housing 12 of the shearvalve 10 illustrated in the previous figures. Again, all of the elementsthat form the downstream housing 12 that have been previouslyillustrated in the preceding figures are shown here and thus are notrepeated.

FIG. 6 illustrates the containment housing 14 of the shear valve 10 froma top angle view perspective to provide an alternative view of thecontainment housing 14 independent of the upstream housing 16 anddownstream housing 12.

FIG. 7 shows the upstream housing 16 independent of the outer housing 14and the downstream housing 12, showing aspects that have been previouslydescribed in the preceding figures and text.

FIG. 8 illustrates a fuel dispenser 110 that may be used in conjunctionwith the shear valve 10 to provide a safety shear valve in the event ofan impact to the fuel dispenser 110. The fuel dispenser 110 is beingshown as a preferred environmental embodiment and use of the shear valve10, but the shear valve 10 is not limited to a fuel dispenserapplication in particular.

The fuel dispenser 110 in FIG. 8 is a typical fuel dispenser that iscomprised of a housing 112. A hose 114 and nozzle 116 are provided sothat fuel carried internal to the fuel dispenser 110 is dispensedthrough the hose 114 and through the nozzle 116 into a vehicle fuel tank(not shown). The fuel dispenser 110 contains a price display 118 and avolume display 120, as is typical for a fuel dispenser 110 and iscommonly known in the art. The fuel dispenser 110 may also contain aninstruction display 122 that provides information and/or instructions tothe customer interfacing with the fuel dispenser 110.

FIG. 9 contains an internal view of some of the components that may becontained inside the fuel dispenser 110, and also illustrates how theshear valve 10 may be used with the fuel dispenser 110. As illustratedin FIG. 9, branch fuel piping 124, which is double-walled fuel piping,extends into the inlet 17 of the shear valve 10 as previously described.In this manner, fuel flowing from the UST from the main fuel piping (notshown) that is coupled to the branch fuel piping 124 is connected to theshear valve 10 so that fuel flows through the flow path 92, 94, 96internal to the shear valve 10.

After the fuel exits the outlet 18 of the shear valve 10, it encountersinternal fuel dispenser piping 126 to the fuel dispenser 110 so that thefuel is carried to various components internal to the fuel dispenser 110for eventual delivery to the hose 114 and nozzle 116 and into avehicle's fuel tank. Again, the internal fuel dispenser piping 126 maybe double-walled piping, such that connection to shear valve 10 providesfor the interstitial space of the internal fuel dispenser piping 126 tobe coupled to the interstitial space 60 of the shear valve 10, which maybe coupled to the interstitial space of the branch fuel piping 124 forthe purposes previously described.

After the fuel enters into the internal fuel piping 126, it mayencounter a flow control valve 128 and meter 138. The valve 128 is underthe control of the control system 134 via a valve control signal line136. In this manner, the control system 134 can control the opening andclosing of flow control valve 128 to either allow fuel to flow or notflow through the meter 138 and on to the hose 114 and nozzle 116. Thecontrol system 134 typically instructs the flow control valve 128 toopen when a fueling transaction is proper and allowed to be initiated.

The flow control valve 128 is contained below a vapor barrier 130 in ahydraulics area 131 of the fuel dispenser 110 where Class 1, Division 1components are provided for safety reasons and in an intrinsically safemanner, as described in U.S. Pat. No. 5,717,564, incorporated herein byreference in its entirety. Control system 134 is typically located in acompartment of the fuel dispenser 110 above the vapor barrier 130 thatdoes not have to be provided in an intrinsically safe housing. After thefuel exits the flow control valve 128, the fuel typically encounters ameter 138 wherein the fuel flow though the meter 138, and the meter 138measures the volume and/or flow rate of the fuel. The meter 138typically contains a pulser (not shown) that generates a pulser signal140 to the control system 134, indicative of the volume and/or flow rateof fuel. In this manner, the control system 134 can update the pricedisplay 118 and the volume display 120, via the price display signalline 144 and the volume display signal line 146, so that the customer isinformed of the price to be paid for the fuel as well as the volume offuel dispensed.

After the fuel exits the meter 138, the fuel is carried in more internalfuel flow piping 142, which is then coupled to a hose 114 typicallylocated in the upper housing or canopy of the fuel dispenser 110 and onto the nozzle 116, as is well known to one of ordinary skill in the art.

In this manner, by the shear valve 10 having the interstitial space 60,as described above, leaks or breaches in the housings 12, 16 of theshear valve 10 are contained in the interstitial space 60 formed by thecontainment housing 14. Further, the interstitial space orifices 40, 62being coupled to the interstitial space 60 of the shear valve 10, allowscoupling of the interstitial space 60 to the interstitial space of thebranch fuel piping 124, so that the interstitial space of the internalfuel dispenser piping 126 can be coupled to the interstitial space ofthe branch fuel piping 124, through the shear valve interstitial space60. This provides one continuous interstitial space between theinterstitial spaces of the branch fuel piping 124, the shear valve 10,and the internal fuel dispenser piping 126 so that the continuous spacecan be monitored as one space for leak prevention and/or detection.

FIG. 10 illustrates an alternative embodiment of the double-walledcontained shear valve 10. The double-walled shear valve 10 in FIG. 10 isillustrated from a front view. Similar to the shear valve 10 illustratedin FIGS. 1-9, the double-walled shear valve 10 in FIG. 10 is comprisedof a downstream housing 12 coupled to the outer housing or containmenthousing 14. The containment housing 14 is coupled to the upstreamhousing 16. An orifice (not shown in FIG. 10) in the upstream housing 16provides an inlet 17 to receive fuel from a branch or main fuel pipingcarrying fuel from a storage tank. The fuel is carried through aninternal fuel flow path of the double-walled shear valve 10. The fuelexits the shear valve 10 through an outlet 18 formed by the orifice 26(shown in FIGS. 12 and 14) within the downstream housing 12. Themounting bosses 20, 22 are attached or provided as part of thecontainment housing 14 to mount the double-walled shear valve 10 inplace when installed in the field.

As illustrated in FIG. 10 and more particularly in FIG. 11, the shearvalve 10 may be fitted with a vacuum actuator 204. The vacuum actuator204 is coupled to the interstitial space 60 (illustrated in FIG. 12) ofthe shear valve 10. The vacuum actuator 204 is designed to apply arotational force to the rotatable shaft 88 to open and close the mainpoppet valve 82 in response to generation or loss of a vacuum level inthe interstitial space 60 within the shear valve 10 or other systemhaving a separate interstitial space (not shown). This separateinterstitial space may be internal fuel dispenser piping 126, branchfuel piping 124, main fuel piping (not shown), a containment sump (notshown) or any other fuel-handling component where a loss of vacuum isindicative of a possible leak. The vacuum actuator 204 is comprised ofan internal vacuum actuation device (not shown) that retracts a vacuumactuator shaft 210 from a vacuum actuator orifice 220 in response togeneration of a sufficient vacuum level. The vacuum actuator 204 isattached to the containment housing 14 of the shear valve 10 via avacuum actuator mounting plate 212. The vacuum actuator mounting plate212 contains two mounting orifices 213. A mounting bolt 214 is placedinside one mounting orifice 213 to secure the plate 212 to thecontainment housing 14. The rotatable shaft 88 that protrudes thecontainment housing 14 fits inside the other orifice 213 and is securedusing another bolt 216.

The vacuum actuator shaft 210 is coupled to an attachment means 216 thatis attached to a lever 208 attached to the rotatable shaft 88. Therotatable shaft 88 is spring biased in a clockwise rotational direction.When a sufficient vacuum level is generated, the vacuum actuator 204pulls the vacuum actuator shaft 210 inward thereby causing the rotatableshaft 88 to rotate counter-clockwise. This opens the main poppet valve82 inside the fuel flow path within the shear valve 10 to allow fuelflow. When the vacuum level is sufficiently lost in the interstitialspace 60, the vacuum actuator 204 moves the vacuum actuator shaft 210outward thereby releasing the energy in the spring biased rotatableshaft 88 causing it to rotate clockwise. This closes the main poppetvalve 82 inside the fuel flow path of the shear valve 10 thereby cuttingoff fuel flow. This is because loss of vacuum level in the interstitialspace 60 in the shear valve 10 is indicative of a leak in either theupstream housing 16, the downstream housing 12, or the containmenthousing 14, which may be due to a shear. Or as discussed above, the lossof vacuum may be in another system where it is desired to close theshear valve 10 in response for safety reasons. It is desired toautomatically close the main poppet valve 82 to close the fuel flow pathin the shear valve 10 when a leak is detected in the form of a vacuumlevel loss.

The double-walled shear valve 10 illustrated in FIG. 11 is attached tothe branch fuel piping 124, as well as the internal fuel dispenserpiping 126. The branch fuel piping 124 may include a flex connectionpiping portion 125 to allow flexibility when attaching the piping 125 tothe double-walled shear valve 10 in the field. Fuel flow from thestorage tank (not shown) travels through fuel piping eventually reachingthe branch fuel piping 124. From there, the fuel enters into thedouble-walled shear valve 10 and exits through the downstream housing 12and into a fuel flow path internal to the fuel dispenser piping 126 whenthe main poppet valve 82 and the secondary poppet valve 98 are open. Thedispenser fuel piping 126 is attached to the downstream housing 12 ofthe double-walled shear valve 10 via fasteners 222. The branch fuelpiping 124 is attached to the upstream housing 16 of the shear valve 10via fasteners 200 that are fitted into orifices 205 and secured tightlyvia bolts 202 (see FIG. 10 as well).

FIG. 12 illustrates a cross-sectional view of the double-walled shearvalve 10 as illustrated in FIG. 10. The upstream housing 16 is comprisedof a uniform body that contains an internal orifice forming an upstreamhousing flow path 92. The thickness of the material comprising theupstream housing 16 provides an inner wall 48 and an outer wall 50.Similarly, the outer or containment housing 14 contains an orificeforming a containment housing flow path 94, wherein the thickness of thecontainment housing 14 forms an inner wall 52 and an outer wall 54.

The containment housing 14 is secured to the upstream housing 16 by athreaded orifice 232 and fastener 234 fitted into a slot 230 in theupstream housing 16 for a flush mount attachment. The fastener 234 isthreaded and contains a fastener head 236 for fastenably rotating thefastener 234 into the threaded orifice 232. An o-ring seal 238 isprovided around the threaded orifice 232 to provide a tight seal betweenthe upstream housing 16 and the containment housing 14 when securelyattached to each other.

When the upstream housing 16 is attached to the containment housing 14,an indention or notch 67 in the inner wall 48 of the upstream housing 16rests against the containment housing 14. The notch 67 is located aroundthe circumference of the inner wall 48 of the upstream housing 16. Ano-ring seal 69 is placed inside the notch 67 to provide a tight sealbetween the top of the upstream housing 16 where the inner wall 48 ofthe upstream housing 16 abuts against the containment housing 14.

Similarly, the downstream housing 12 is securely attached to thecontainment housing 14 via a fastener orifice 242 provided in thecontainment housing 14. A fastener 290 (illustrated in FIG. 18) isplaced inside the orifice 36 in the downstream housing 12 aligned withthe fastener orifice 242. The fastener 290 is threaded and is screwedinto the fastener orifice 242 to securely attach the downstream housing12 to the containment housing 14. Similar to notch 67, the containmenthousing 14 contains an indention or notch 81 located around thecircumference of the containment housing 14 where the inner wall 52 ofthe containment housing 14 abuts the downstream housing 12. An o-ringseal 83 is placed inside the notch 81 to provide a tight seal.

The downstream housing 12 also has an indention or notch 72 locatedaround the circumference of the inner wall of the downstream housing 12.An o-ring seal 74 is placed inside the notch 72 to provide a tight sealbetween the inner wall of the downstream housing 12 and the outer wall50 of the containment housing 14.

When the upstream housing 16 and the downstream housing 12 are securedto the containment housing 14 in this manner, an interstitial space 60is formed between the outer wall 50 of the upstream housing 16 and theinner wall 52 of the containment housing 14. The containment housing 14provides an interstitial space orifice 61 that is fluidly coupled to theinterstitial space 60 formed between the inner wall 52 of thecontainment housing 14 and the outer wall 68 of the downstream housing12. In this manner, one contiguous interstitial space 60 surrounds theouter wall 50 of the upstream housing 16 and the outer wall 68 of thedownstream housing 12 (i.e. the fuel flow paths 92, 94, 96) to containleaks and/or to allow vacuum or pressure level monitoring of theinterstitial space 60.

The containment housing 14 also contains the shear groove 78 along thecircumference of the outer wall 54 to provide a shearing point for thedouble-walled shear valve 10 to break or shear in a controlled fashionwhen impacted. In the event of a shear at the shear groove 78, fuelcaptured inside the interstitial space 60 may leak outside thecontainment housing 14 through the shear groove 78. Therefore, althoughnot illustrated in FIG. 12, the leak skirt 19 like that illustrated inthe double-walled shear valve 10 of FIG. 3 may be provided although notrequired.

The downstream housing 12 contains an orifice that forms a downstreamhousing fuel flow path 96. The downstream housing fuel flow path 96 isfluidly coupled to the containment housing flow path 94 and the upstreamhousing flow path 92 when the main poppet valve 82 and the secondarypoppet valve 98 are open. The fuel flow paths 92, 94, 96 form one flowpath to allow fuel to flow from the branch fuel piping 124 through theshear valve 10 and out to the internal fuel dispenser piping 126 duringnormal operation.

The double-walled shear valve 10 contains the main poppet valve 82 thatcontrols opening and closing of the upstream housing flow path 92 to thecontainment housing flow path 94 to allow fuel to flow therethrough. Themain poppet valve 82 is comprised of a main poppet valve head 84 thatrests against a main poppet valve seat 90 formed around the orifice inthe containment housing 14 forming the containment housing fuel flowpath 94. When the main poppet valve 82 is closed, fuel flow is preventedfrom flowing from the upstream housing fuel flow path 92 to thecontainment housing fuel flow path 94.

One aspect of the invention and the shear valve 10 illustrated in FIG.12 provides an improved main poppet valve 82 that requires less force toopen. This is particularly important when using a vacuum actuator 204 toautomatically apply a rotational force to the rotatable shaft 88 to openthe main poppet valve 82 when a sufficient vacuum level is restored inthe interstitial space 60. A vacuum actuator 204 may not be able togenerate enough rotational force to rotate the rotatable shaft 88 when alarge pressure differential exists across the main poppet valve 82. Or,using the vacuum actuator 204 with greater force ranges may be tooexpensive for practical inclusion in the shear valve 10.

For example, if there is pump pressure trapped in the upstream streamhousing fuel flow path 92 and little or no pressure or atmosphericpressure in the containment housing fuel flow path 94, a large force isrequired open the main poppet valve 82. It would not be uncommon for a50 p.s.i. pressure drop to be present across the main poppet valve 82.Depending on the diameters, areas of the main poppet valve head 84 couldhave anywhere from 1.7 to two times 50 psi of force required to move themain poppet valve head 84 away from the main poppet valve seat 90 tothereby opening the main poppet valve 82.

In order to provide a main poppet valve 82 that can be opened with lessforce, so that a sufficient and/or less expense vacuum actuator 204 maybe used to open the main poppet valve 82, the main poppet valve 82includes a main poppet valve head 84 that is attached to a main poppetvalve support 259. The main poppet valve support 259 contains a mainpoppet valve support orifice 253 formed by an inner diameter tube 254formed as part of the same component. The inner diameter tube 254 has aninner diameter orifice 255 coupled to the containment housing fuel flowpath 94. The inner diameter seal 252 seals off an inner diameter orifice255 from the upstream housing fuel flow path 92. The main poppet valvehead 84 is attached around the circumference of the inner diameter tube254 via a retaining ring 260. The inner diameter seal 252 rests against,but is unconnected, to the main poppet valve support 259 and is attachedto a flapper 246 via a washer 247 and attachment means 250. When theinner diameter seal 252 is cracked, the pressure differential betweenthe containment housing fuel flow path 94 and the upstream housing fuelflow path 92 starts to equalize. Thereafter, it is easier and requiresless force to lift the main poppet valve head 84 off of the main poppetvalve seat 90 to open the main poppet valve 82.

A flapper 246 is attached to the rotatable shaft 88. The flapper 246 iscomprised of a flapper ledge 248 containing two flapper orifices 256that surround two main poppet valve shafts 257 mounted perpendicularlyto the main poppet valve support 259. When the flapper 246 rotates in acounter-clockwise direction, via the vacuum actuator 204 rotating therotatable shaft 88 in a counter-clockwise direction, the flapper 246 andits flapper orifices 256 move down about the main poppet valve shafts257. This cause the inner diameter seal 252 to open first, lifting downoff of the main poppet support 259 and opening the main poppet supportorifice 253. This couples the inner diameter orifice 255 to the upstreamhousing fuel flow path 92 to begin to equalize any pressure differentialbetween the containment housing fuel flow path 94 and the upstreamhousing fuel flow path 92. Less force is required to overcome thepressure differential between the inner diameter orifice 255 and theupstream housing fuel flow path 92 than would otherwise be required toovercome the pressure differential between the containment housing fuelflow path 94 and the upstream fuel flow path 92.

Thus, providing the inner diameter orifice 255 reduce this pressuredifferential and allows a less powerful vacuum actuator 204 to open theinner diameter seal 252. Thereafter, the flapper 246 continues to rotatecounter-clockwise until the flapper ledge 248 rests against protrudingportions 258 of the main poppet valve shafts 259. Once this occurs, themain poppet valve shaft 257 pulls against the main poppet valve support90 thereby pulling the main poppet valve head 84 away from the mainpoppet valve seat 90 to open the main poppet valve 82. Opening the mainpoppet valve 82 couples the upstream fuel flow path 92 to thecontainment housing fuel flow path 94 to allow fuel to flow through theshear valve 10.

FIG. 13 illustrates the flapper 246 in larger detail. As shown, theflapper ledge 248 will eventually contact and push downward on the mainpoppet valve shaft protrusions 258 after the inner diameter seal 252 isopened. Because the inner diameter seal 252 has opened thereby openingthe main poppet valve support orifice 253 and coupling the containmentfuel flow path 94 to the upstream fuel flow path 92, less force isrequired to be applied by the flapper ledge 248 to pull down on the mainpoppet valve support 259 thereby pulling the main poppet valve seat 84from the main poppet valve seat 90 to open the main poppet valve 82.FIG. 14 illustrates the main poppet valve 82 fully opened.

Turning back to FIG. 12, after the fuel reaches the containment housingfuel flow path 94 due to the main poppet valve 82 being opened, the fuelflow next encounters a conical rib support 262 that contains orifices267 there around to allow fuel flow to pass therethrough. The conicalrib support 262 props open the secondary poppet valve 98 to allow fuelflow to pass therethrough and into the downstream fuel flow path 96 foreventual exit out of the orifice 18 of the double-walled shear valve 10.The conical rib support 262 is supported by the containment housing 14.The legs of the conical rib support 263 rest and are contained insidethe indention or notch 260 that is located around the circumference ofthe containment housing 14 in the containment housing fuel flow path 94.A retaining ring 265 holds the conical rib support 262 in place.

The secondary poppet valve 98 contains a secondary poppet support 101having a perpendicular shaft member 279 that rests against a spring 263.The spring 263 rests between the secondary poppet support 101 and a stopor upstream housing retaining member 266 comprised of ribs 268 providingorifices to allow fuel to flow there through. The stop 266 is held inplace via indention or notch 264 that is contained along thecircumference of the downstream housing 12 in the downstream housingfuel flow path 96. The shaft member 279 protrudes through and movesalong a center orifice within the retaining member 266. The secondarypoppet head 100 is designed to rest against the secondary poppet seat102 when the secondary poppet valve 98 is closed. The conical ribsupport 262 pushes upward against the secondary poppet valve 98 toextend its shaft 264 upward to keep the secondary poppet valve 98 openand from resting against the secondary poppet valve seat 102, therebycoupling the containment housing fuel flow path 94 to the upstreamhousing fuel flow path 96. The conical rib support 262 will remain withthe containment housing 14 in either a damaged or undamaged state in theevent of a complete shear or separation of the downstream housing 12from the containment housing 14. In either event, such separation willcause the secondary poppet valve 98 to be pushed downward to restagainst the secondary poppet valve seat 102 to close the secondarypoppet valve 98. In this manner, fuel resident in the downstream housingfuel flow path 96 or in the fuel dispenser piping 126 coupled to theshear valve 10 will not flow back past the secondary poppet valve 98,and thus possibly leak through the damaged shear valve 10 or sheargroove 78 when a shear or other impact occurs.

FIG. 15 illustrates a perspective view of the downstream housing 12 ofthe double-walled shear valve 10 illustrated in FIGS. 10 through 14. Theupstream housing 16 and containment housing 14 are not attached to thecontainment housing 14 in this figure.

As illustrated, an orifice 18 is provided to allow fuel to flowtherethrough through the downstream housing 12 and to exit thedouble-walled shear valve 10. The interstitial space orifices 40 areshown such that when the downstream housing 12 is attached to thecontainment housing 14, the interstitial space orifices 40 are fluidlycoupled to the interstitial space 60 provided between the outer wall 68of the downstream housing 12 and the inner wall 52 of the containmenthousing 14. The orifices 36 are provided in the downstream housing 12 toattach the downstream housing 16 to fuel dispenser piping 126, asillustrated in FIG. 11. Fasteners 222 are inserted into the orifices 36to secure the two together as illustrated in FIG. 11.

FIG. 16 illustrates a perspective view of the containment housing 14 ofthe double-walled shear valve 10 illustrated in FIGS. 10 through 14. Thethird mounting boss 44 is shown in this figure. The upstream housing 16and the downstream housing 12 are not attached to the containmenthousing 14 in this figure. A port 277 is provided through the body ofthe containment housing 14 to allow coupling via a tube or pipe (notshown) to the interstitial space 60 for vacuum or pressure levelmonitoring purposes, as previously discussed above. Orifices 242 thatreceive fasteners 290 (see FIG. 18) via orifices 36 are illustrated.

FIG. 17 illustrates a prospective view of the upstream housing 16 of thedouble-walled shear valve 10 illustrated in FIGS. 10 through 15. Thecontainment housing 14 and the downstream housing 12 are not attached tothe upstream housing 12 in this figure. A port 271 having a port orifice273 is shown and provided for the rotatable shaft 88 to fit inside toopen and close the main poppet valve 82 as describe above.

FIG. 18 illustrates the double-walled shear valve 10 as illustrated inFIGS. 10 through 15 coupled to the dispenser fuel pipe 126. Thedispenser fuel piping 126 is comprised of an outer piping 280surrounding by an inner piping 282. An interstitial space 284 is formedbetween the inner piping 282 and the outer piping 280. The interstitialspace 284 extends partially through the dispenser fuel piping 126 and isterminated at a termination point 286. The interstitial space 284 of thefuel dispenser piping 282 is coupled to the interstitial space 60 of thedouble-walled shear valve 10 by the attachment of the fuel dispenserpiping 282 to the downstream housing 12. This is so the interstitialspace 284 of the fuel dispenser piping 126 and the interstitial space 60of the shear valve 10 form one contiguous interstitial space 60, 284 tobe monitored as one zone or space. As previously described, a vacuum orpressure level generated inside the interstitial space 60, 284 can bemonitored for leaks. Further, the vacuum actuator 204 will cause themain poppet valve 82 to close if a leak occurs in either the shear valve10 or the fuel dispenser piping 126 and as described in the '504application. The interstitial space orifice 40 is coupled to a circulargrooved indention 61 formed in the top of the downstream housing 12,which couples to the interstitial space 284 of the fuel dispenser piping282 when attached to the downstream housing 12.

FIG. 19 illustrates an alternative embodiment of the double-walled shearvalve 10 illustrated in FIGS. 10 through 15. All design details of theshear valve 10 illustrated in FIG. 19 are the same as the shear valve inFIGS. 10 through 15 with the exception. The interstitial space orifices40 and circular grooved indention 61 are not provided in the downstreamhousing 12. In this manner, the interstitial space 60 of thedouble-walled shear valve 10 is blocked off and cannot not extendthrough the downstream housing 12 of the double-walled shear valve 10when attached to fuel dispenser piping 126 even if the fuel dispenserpiping 126 contains an interstitial space 284 like that illustrated inFIG. 18. In this manner, only the interstitial space 60 of the shearvalve 10 controls the vacuum actuator 204. A monitoring system designedto generating and/or monitor a vacuum or pressure level in theinterstitial space 60 for leaks cannot be used for the fuel dispenserpiping interstitial space 284 unless the shear valve 10 illustrated inFIG. 19 is used in an unintended and/or unauthorized manner.

FIG. 20 illustrates a perspective view of the modified downstreamhousing 12 used with the double-walled shear valve 10 illustrated inFIG. 18. Note that the interstitial space orifices 40 are not providedlike that included in the downstream housing 12 illustrated in FIG. 15.

Those skilled in the art will recognize improvements and modificationsto the preferred embodiments of the present invention. All suchimprovements and modifications are considered within the scope of theconcepts disclosed herein and the claims that follow.

1. A shear valve that carries fuel from a branch or main fuel piping tofuel dispenser piping, comprising: a housing having an axial lengthextending between a first end and a second end thereof, said housingdefining a shear groove on the outside circumference of the housing,said housing being initially unbroken at said shear groove but breakableat said shear groove in response to a shearing force; the housingcontaining an orifice therein forming a fuel flow path; a main poppetvalve coupled to the housing that is adapted to close the fuel flow pathto prevent flow of fuel; and a flexible leak skirt fixed to an exteriorof the housing at a first location upstream of said shear groove and asecond location downstream of said shear groove, said leak skirtsurrounding the unbroken shear groove but not surrounding a remainder ofsaid housing along said axial length thereof further upstream anddownstream of said first and second locations to provide a leakcontainment chamber to contain fuel leaking through the shear groove inthe event of a leak that subsequently occurs at the shear groove due toa break at said shear groove.
 2. The valve of claim 1, wherein said leakskirt comprises an elastic material.
 3. The valve of claim 2, whereinthe housing contains a main poppet valve seat along the orifice adaptedto seat the main poppet valve when closed to close the fuel flow path.4. The valve of claim 3, wherein the main poppet valve is adapted toclose off an upstream fuel flow path from the housing fuel flow path inresponse to a shear.
 5. The valve of claim 4, further comprising asecondary poppet valve and secondary poppet valve seat coupled to thehousing, said secondary poppet valve adapted to close off a downstreamfuel flow path from the housing fuel flow path in response to a shear.6. The valve of claim 1, wherein said leak skirt comprises an elastomermaterial.
 7. The shear valve of claim 1, wherein said housing includesan upstream housing and a separate downstream housing connectedtogether.
 8. A shear valve for use with a fuel dispenser, comprising: ahousing having an axial length extending between a first end and secondend thereof, said housing defining a shear groove on the outsidecircumference of the housing, said housing being initially unbroken atsaid shear groove but breakable at said shear groove in response to ashearing force; the housing containing an orifice therein forming a fuelflow path; a main valve coupled to the housing that is adapted to closethe fuel flow path to prevent flow of fuel, wherein the main valve isadapted to close off an upstream fuel flow path in response to a shear,and wherein the housing contains a main valve seat along the orificeengaged by the main valve when closed; a flexible leak skirt fixed to anexterior of the housing at a first location upstream of said sheargroove and a second location downstream of said shear groove andcomprising an elastomer material, said leak skirt surrounding theunbroken shear groove but not surrounding a remainder of said housingalong said axial length thereof further upstream and downstream of saidfirst and second locations to provide a leak containment chamber tocontain fuel leaking through the shear groove in the event of a leakthat subsequently occurs at the shear groove due to break at said sheargroove; and a secondary poppet valve and secondary poppet valve seat inthe housing, said secondary poppet valve adapted to close off adownstream fuel flow path from the housing fuel flow path in response toa shear.
 9. The shear valve of claim 8, wherein said housing includes anupstream housing and a separate downstream housing connected together.10. The shear valve of claim 8, wherein said main valve is a flapper.11. The shear valve of claim 10, wherein said flapper is spring-loaded.12. A shear valve that carries fuel from a branch or main fuel piping tofuel dispenser piping, comprising: a housing defining a shear groove onthe outside circumference of the housing, said housing being initiallyunbroken at said shear groove but breakable at said shear groove inresponse to a shearing force; the housing containing an orifice thereinforming a fuel flow path; a main poppet valve coupled to the housingthat is adapted to close the fuel flow path to prevent flow of fuel; aflexible leak skirt coupled to an exterior of the housing, said leakskirt surrounding the unbroken shear groove to provide a leakcontainment chamber to contain fuel leaking through the shear groove inthe event of a leak that subsequently occurs due to a break at saidshear groove; and wherein said housing defines a containment housing andan inner housing coupled to the containment housing, and partially orfully surrounded by the containment housing, such that an interstitialspace is formed separate from the fuel flow path between the containmenthousing and the inner housing.
 13. A shear valve for use with a fueldispenser, comprising: a housing defining a shear groove on the outsidecircumference of the housing, said housing being initially unbroken atsaid shear groove but breakable at said shear groove in response to ashearing force; the housing containing an orifice therein forming a fuelflow path; a main valve coupled to the housing that is adapted to closethe fuel flow path to prevent flow of fuel, wherein the main valve isadapted to close off an upstream fuel flow path in response to a shear,and wherein the housing contains a main valve seat along the orificeengaged by the main valve when closed; a flexible leak skirt coupled toan exterior of the housing comprising an elastomer material, said leakskirt surrounding the unbroken shear groove to provide a leakcontainment chamber to contain fuel leaking through the shear groove inthe event of a leak that subsequently occurs at the shear groove due tobreak at said shear groove; a secondary poppet valve and secondarypoppet valve seat in the housing, said secondary poppet valve adapted toclose off a downstream fuel flow path from the housing fuel flow path inresponse to a shear; and wherein said housing defines a containmenthousing and an inner housing coupled to the containment housing, andpartially or fully surrounded by the containment housing, such that aninterstitial space is formed separate from the fuel flow path betweenthe containment housing and the inner housing.